Cassette recorders are generally provided with feelers which disable the record function when they enter an opening in the wall of a cassette. An unrecorded cassette may have a tab at that opening which the user may break out after making a recording, thus preventing accidental erasure. After breaking out the tab, the opening may be covered with tape to make a new recording. Some cassettes have built-in slides which can be moved repeatedly to cover and uncover the record-disable opening.
"Specifications for 8 mm Video Cassette" dated March 1983 have been distributed by Electronic Industries Association of Japan. Those specifications show a record-disable opening called "mis-erasure protection hole", and five openings called "recognition holes", all in the broad wall of the lower shell of the cassette. Each of the recognition holes is originally closed by a breakout tab, called "removable piece" in the specifications. The removable piece may be a disk integrally molded with the base shell and recessed 1.2 mm beneath the exterior face of its broad wall. If punched out from beneath the cassette, the disk would tend to remain loose within the cassette and might later block one of the recognition holes. Since the disk after being punched out tends to at least equal the diameter of its hole, it would be difficult to design a punch that would hold the disk for retrieval through the recognition hole.
To avoid such problems, many potential manufacturers of the 8 mm video cassette are leaving corresponding holes in the broad wall of the cover shell in order to punch out each removable piece from the top. It would be esthetically more pleasing to avoid these holes in the cover shell.